This invention relates generally to respiratory inhalers of the type used to deliver a selected medication in aerosol form to a patient, wherein the medication is drawn by inhalation directly into the lungs of the patient. More specifically, this invention relates to an improved inhaler of relatively compact and simplified construction, wherein the inhaler is vented for breath coordinated inhalation of air and medication in a regulated timed manner, but further wherein entry of contaminants into the inhaler between uses is substantially prevented.
Respiratory inhaler devices are generally known in the art for administering a selected medication typically in aerosol form directly into the lungs of a patient to treat a wide variety of medical conditions, such as asthma, bronchitis, and the like, and also for treating other nonrespiratory conditions wherein the lungs represent the site-of-delivery for a selected medication. In one common form, the inhaler comprises a compact hand-held housing for receiving and supporting a cannister containing the selected medication in liquid form under pressure. The cannister is equipped with a reciprocal valve assembly adapted for depression to deliver a single metered dose of the medication through a spray nozzle which propels the medication in aerosol form through a mouthpiece for direct inhalation by the patient. In use, the patient places the mouthpiece in his or her mouth and attempts to inhale in timed relation to manipulation of the cannister and housing to depress the valve assembly, in an effort to draw a substantial portion of the medication deeply into the lungs.
To enhance the delivery of the medication to the patient's lungs, breath coordinated inhalers have been developed wherein air is drawn by the patient through the inhaler housing in synchronized relation to the delivery of the medication. That is, by allowing air to flow through the housing and to be inhaled as the medication is sprayed, the medication can be entrained within a substantial volume of air for better ingestion into the lungs and resultant better administration of the medication. However, the provision of an air pathway through the inhaler housing also provides an open housing construction that is highly susceptible to entry of dirt and other contaminants between uses to administer the medication. In this regard, between uses, the inhaler is often carried about by the patient in a pocket or purse whereat undesired entry of contaminants into the inhaler housing is likely to occur.
Attempts to reconfigure the inhaler housing to accommodate breath coordinated inhalation yet reduce or eliminate undesired entry of contaminants between uses has met with limited success. Vented inhaler housings designed to restrict ingress of contaminants between uses have been relatively complex and thus relatively costly in construction, and further have typically resulted in a substantial increase in the overall size and shape of the inhaler housing. Moreover, absent a substantial increase in the size and shape of the inhaler housing, such vented housings have not provided a simple and reliable way to provide a uniform stroke length for the cannister valve assembly to correspondingly provide uniform doses of the medication, notwithstanding cannister dimension and tolerance variations which occur during normal manufacture.
There exists, therefore, a continuing need for further improvements in breath coordinated inhalers, particularly with respect to providing a relatively simple and compact and cost effective inhaler housing construction that is substantially closed to entry of contaminants between uses, and further wherein the compact inhaler housing is designed to accommodate dimensional variations in the medication-containing cannister. The present invention fulfills these needs and provides further related advantages.